The present invention relates to a method of estimating for evaluation a failure occurrence likelihood (real ability) of a manufacturing workshop upon manufacturing electric/electronic apparatuses for home use, products (or articles) for office-automation (OA) and the like by assembling or processing component parts therefor and an apparatus for carrying out the method, and additionally the invention concerns a product quality evaluation method for evaluating quality such as work-related fraction defective or work-related defective ratio and the like of products or articles such as those for home use, office automation (OA) and the like which are manufactured by assembling or processing component parts therefor and an apparatus for carrying out the method, and furthermore the invention concerns a recording medium storing therein a program or programs for executing the estimation/evaluation methods.
Most of the techniques known heretofore in this field are directed to estimation of causes for occurrence of failures or detects on the basis of phenomena which have actually taken place. As the hitherto known techniques for estimating the causes for the failures on the basis of the contents of phenomena actually taken place at the manufacturing stage, there can be mentioned the technique disclosed in JP-A-1-167631 (hereinafter referred to as the prior art 1) and JP-A-6-196900 (hereinafter referred to as the prior art 2). In the prior art 1, there is disclosed a work readjusting method according to which causes for failures or defects are defined in correspondence to combinations of passable/impassable items after inspection or examination of works, whereon degrees of correlation between the combinations of the passable/impassable items and the causes for failures or defects are estimated by taking into account remedying measures as taken, to thereby determine the cause for failure or defect on the basis of the degree of correlation between the combinations of passable/impassable items and the causes for failure or defect as estimated, whereon the cause for failure or defect as determined is removed by taking proper measures pertinent to the cause for failure or defect as determined. On the other hand, in the prior art 2, a method of analyzing defect factors in an electronic part packaging process is described, according to which quality data inputted at printing! mounting/soldering steps, respectively, in the electronic part packaging process are compared on a printed-circuit-board basis, to determine arithmetically the degree of influence of each of the above-mentioned steps exerted to the defectiveness of the finished product by referencing quality defectiveness regulation rules indicating possibilities of occurrence of defects in the individual steps.
Further, as the failure diagnosis techniques in which similar techniques are adopted, there may be mentioned, for example, those disclosed in JP-A-7-13517 (hereinafter referred to as the prior art 3) and JP-A-7-271587 (hereinafter referred to as the prior art 4). In the prior art 3, a method of estimating causes for unfavorable events is described, according to which phenomena representing statuses of unfavorable events and causes bringing about such unfavorable phenomena are compared on a phenomenon-by-phenomenon-basis for creating an association table in which there are defined association values indicating degrees of associations between phenomena and the relevant causes therefor, respectively, wherein phenomena taking place in accompanying an unfavorable event are discriminated and then values derived by weighing the association values relevant to the phenomena in accordance with a predetermined method are accumulatively summed up, and the cause for which the sum value is maximum is decided as the cause for the unfavorable event by referencing the association table. On the other hand, in the prior art 4, a failure diagnosis apparatus is described which is so arranged that a hypothesis is framed by investigating unfavorable phenomenon by making use of knowledge database stating definitely causes for failures and unfavorable phenomena, whereon the hypothesis mentioned above is verified by resorting to a knowledge database implemented by analyzing theoretically the causality relations between the unfavorable phenomena and the causes therefore.
All of the prior arts 1, 2, 3 and 4 mentioned above are directed to the techniques for estimating the causes having direct influence to the failure or defect event on the basis of the phenomena taken place actually in the past for allowing the proper remedying or repairing measures to be taken speedily at the time point of occurrence of failure phenomenon on the basis of the event actually taken place.
On the other hand, as a method or procedure for performing in advance a quality evaluation of an article to be manufactured before failure has actually occurred, there is known an FMEA (Failure Mode and Effects Analysis) technique (described in NIRKAGIREN: Reliability Engineering Ser. 7 xe2x80x9cPRACTICAL USE OF FMEA, FTAxe2x80x9d) which is primarily adopted at the stage of designing a product or article to be manufactured. According to this procedure, an evaluator himself or herself predicts failure phenomena which may occur in association with individual component parts constituting a product and summarizes the xe2x80x9cfailure phenomena relating to the individual parts in the form of a table. Thus, by referencing the table, the evaluator himself or herself can predict xe2x80x9cwhat sort of influence a product to be manufactured will suffer when a failure takes placexe2x80x9d. In this way, high-quality design having substantially no unintentional omissions can be realized.
Further, in conjunction with the FMEA method, there is known a procedure for estimating the degree of seriousness of defects and failures relating to individual component parts by determining the probability of occurrence of failure phenomena (defective ratios) as estimated by the evaluator in conjunction with the individual parts, whereon the degree of seriousness of defect of the product to be manufactured which can be regarded as being ascribable to the defect(s) of the individual parts is estimated, as in the case of FMECA (Failure Mode, Effects and Criticality Analysis) technique.
Additionally, there are known so-called subcontractor factory inspection/check sheet schema adopted generally by various enterprises for checking the subcontractors"" factories for evaluating the factories"" facility levels capable of manufacturing products of quality to be satisfied. Further, as other techniques for evaluating the productivities of the factories, there are known xe2x80x9cfactory diagnosis apparatusxe2x80x9d (JP-A-9-62309) (prior art 5), and xe2x80x9cdiagnosis system for factories for packaging worksxe2x80x9d (JP-A-10-79599) (prior art 6).
However, none of the conventional methods or techniques mentioned above, i.e., the techniques for estimating the causes exerting influences straightforwardly to the failures or defects on the basis of the events which took place in the past, the FMEA method and the FMECA method, is not in the position to estimate the potential of failure to occur in a given product with high accuracy, because of the necessity to grasp substantially whole of the failure phenomena which may actually occur.
Such being the circumstances, in the current state of the art, not a few failures actually take place in the manufacturing works due to omission of examination and study, presenting one of the causes for deterioration of the quality of the manufactured articles.
Further, the subcontractor factory inspection! check sheet schema mentioned previously is inherently designed for evaluating organization and system of the factory under evaluation as to the facilities for the development, manufacture, quality securement and the like. However, it is impossible to estimate quantitatively the failure occurrence likelihood of the factory under evaluation on the basis of the results of the evaluation. Furthermore, with the prior art 5 and 6 which are designed for evaluating the productivity of the factory, the evaluation as to the failure occurrence likelihood in the manufacturing workshop is also impossible.
As is apparent from the above, none of the prior techniques which are directed to the manufacturing workshops as described above has adequate faculty for evaluating quantitatively the failure occurrence likelihood of the manufacturing workshop. Thus, great difficulty will be encountered in evaluating, for example, two given factories as to which of them has higher failure occurrence likelihood.
With the present invention, it is contemplated to solve the problems described above by providing a product quality evaluating method which makes it possible to evaluate/estimate the failure occurrence likelihood of a manufacturing workshop (including a factory) which is scheduled to manufacture a given product by performing manufacturing works such as assembling, processing and/or the like at a premanufacturing stage such as a designing stage, a manufacturing process planning stage or the like, to thereby allow the quality such as, for example, work-related defective ratio and the like of the given product to be manufactured through a series of manufacturing works in the above-mentioned manufacturing workshop. With the present invention, it is also contemplated to provide an apparatus for carrying out the method mentioned above and a recording medium for storing the same.
Another object of the present invention is to provide a method of evaluating the failure occurrence likelihood of a manufacturing workshop, which method makes it possible to evaluate/estimate failure occurrence likelihood of a manufacturing workshop (including a factory) which is scheduled to manufacture a given product by performing manufacturing works such as assembling and/or the like at a pre-manufacturing stage such as a designing stage, a manufacturing process planning stage. With the present invention, it is equally contemplated to provide an apparatus for carrying out the method mentioned above and a recording medium storing the same.
For achieving the objects mentioned above, the present invention provides a method and an apparatus for evaluating a failure occurrence likelihood of a manufacturing workshop which feature a workshop database preparation process for creating in advance a workshop evaluating database to be stored for preparation, which database indicates correspondence relations between a plurality of workshop-conditioned failure influential items set previously and failure occurrence ratio indexes at least for standard manufacturing works at standard workshop facility levels for the workshop-conditioned failure influential items, respectively, and a workshop evaluating process for extracting from the workshop evaluating database prepared in the workshop database preparation process those failure occurrence ratio indexes which correspond to workshop facility levels of an inputted evaluation-undergoing manufacturing workshop for the workshop-conditioned failure influential items thereof, respectively, wherein the extracted failure occurrence ratio indexes are to realized over a plurality of concerned workshop-conditioned failure influential items to determine arithmetically the indexes indicating the failure occurrence ratios for the standard manufacturing works, respectively, in the evaluation-undergoing manufacturing workshop, to thereby evaluate/estimate the failure occurrence likelihood (fraction defective) in the manufacturing workshop undergoing the evaluation.
Further, the present invention features a workshop facility level inputting process for inputting at least workshop facility levels of the evaluation undergoing manufacturing workshop for the workshop-conditioned failure influential items, respectively. Further, the present invention features that the aforementioned workshop evaluating database created in the workshop database preparation process of the method and apparatus for evaluating the failure occurrence likelihood of the manufacturing workshop described previously is such a database which indicates correspondence relations between workshop-conditioned failure influential items set previously concerning worker(s), manufacturing equipment, manufacturing conditions, physical environment for manufacturing and management on one hand and on the other hand failure incurrence indexes representing failure occurrence suppressing abilities, failure coping time rate indexes representing failure occurrence coping abilities and defective extraction indexes representing failure detecting abilities for standard manufacturing works, respectively, at least at standard workshop facility levels for the workshop-conditioned failure influential items, respectively.
Furthermore, the present invention features that in the workshop evaluation process of the method and apparatus for evaluating the failure occurrence likelihood of the manufacturing workshop described previously, the three extracted indexes are totalized to thereby arithmetically determine indexes indicating failure occurrence ratios for the workshop-conditioned failure influential items, respectively, and that the arithmetically determined indexes indicating the failure occurrence ratios are totalized over a plurality of concerned workshop-conditioned failure influential items to thereby determine arithmetically the indexes indicating the failure occurrence ratios for the standard manufacturing works, respectively, in the evaluation-undergoing manufacturing workshop.
Furthermore, the present invention features that in the workshop evaluation process of the method and apparatus for evaluating the failure occurrence likelihood of the manufacturing workshop described previously, the workshop-conditioned failure influential items are mutually imparted with relative weights.
Furthermore, the present invention features that in the workshop database preparation process of the method and apparatus for evaluating the failure occurrence likelihood of the manufacturing workshop described previously, the workshop-conditioned failure influential items concerning the worker(s), the manufacturing equipment, the manufacturing conditions, the physical environment for manufacturing and the management are each subclassified into a plurality of items for each of the worker(s), the manufacturing equipment, the manufacturing condition, the physical environment for manufacturing and the management, respectively.
Furthermore, the present invention features that the method and apparatus for evaluating the failure occurrence likelihood of the manufacturing workshop described previously further includes an output process for outputting results (workshop failure occurrence likelihood index, results of evaluation concerning evaluation category-based workshop facility, improvement advices, etc.) of evaluation/estimation as executed by the workshop evaluating process.
Furthermore, the present invention provides a method and apparatus for evaluating a quality of a product, which feature a workshop database preparation process for creating in advance a workshop evaluating database to be stored for preparation, which database indicates correspondence relations between a plurality of workshop-conditioned failure influential items set previously and failure occurrence ratio indexes at least for standard manufacturing works at standard workshop facility levels for the workshop-conditioned failure influential items, respectively, a workshop evaluation process for extracting from the workshop evaluating database prepared in the workshop database preparation process those failure occurrence ratio indexes which correspond to workshop facility levels of an inputted manufacturing workshop for the workshop-conditioned failure influential items thereof, respectively, wherein the failure occurrence likelihood (workshop supplementary constant (workshop-related fraction defective)) for the standard manufacturing works in the manufacturing workshop by totalizing the above-mentioned extracted failure occurrence ratio indexes over a plurality of concerned workshop-conditioned failure influential items to thereby determine arithmetically the indexes indicating the failure occurrence ratios for the standard manufacturing works (typified by simplest downward-movement work in the case of an assembling work), respectively, in the manufacturing workshop, results of the evaluation and estimation being stored as a workshop index in a product evaluating database, and a product evaluating process for evaluating/estimating a quality indicating a work-related defective ratio of a product manufactured through a plurality of manufacturing works in the above-mentioned manufacturing workshop by using the workshop index concerning the manufacturing workshop as stored in the product evaluating database in the above-mentioned workshop evaluating process.
Furthermore, the present invention features that the aforementioned method of evaluating a quality of a product and the aforementioned apparatus for carrying out the same further includes a product database preparation process for storing in advance for preparation in a product evaluating database the indexes indicating fractions defectives in a plurality of mutually differing standard manufacturing operations, respectively, and supplementary indexes which are based on properties of component parts involved in the standard manufacturing operations, respectively, and a product input process for inputting standard manufacturing operations inclusive of properties of the component parts involved in individual manufacturing works, respectively, over a plurality of manufacturing works for manufacturing a product, wherein in the aforementioned product evaluating process, the indexes indicating the fractions defectives and the supplementary indexes (supplementing coefficients) are extracted from the product evaluating database prepared in the product database preparation process on the basis of the standard manufacturing operations inclusive of~the properties of the component parts in the individual manufacturing works as inputted in the product input process, and wherein the extracted indexes indicative of the fractions defectives are supplemented with the extracted supplementary indexes mentioned above and the supplementarily corrected indexes indicating the fractions defectives are synthesized throughout a plurality of manufacturing works, whereon the synthesized index indicative of the fraction defective or the index indicative of the above-mentioned individual extracted fraction defectives is supplementarily corrected with the workshop index (workshop supplementary constant) stored in the aforementioned workshop evaluating process for thereby evaluating estimating the quality of the aforementioned product indicative of the work-related defective ratio.
Further, the present invention provides a recording medium which features that a program for executing the manufacturing workshop failure occurrence likelihood evaluating method or the product quality evaluating method is recorded on the recording medium.
As is apparent from the foregoing description, with the arrangements described above, the failure occurrence ratio in manufacturing a product is determined in dependence on the structural conditions of the product to be manufactured and the workshop conditions or statuses of the manufacturing workshop where the product is to be manufactured.
Thus, the estimated value of the fraction defective ascribable to the assembling or processing is to be arithmetically determined on the basis of the information concerning the factors which exert influence to the probability that a human being or worker can not perform the operations involved in the manufacturing work without fail (hereinafter referred to as the uncertainty). Of the factors which exerts influence to the probability that the human being or worker is incapable of performing the operations involved in the manufacturing work without fail, there exist roughly two types of factors, i.e., one is difficultness of the manufacturing work due to the structure of the product and the other is the environment of the workshop. Such being the circumstances, the present invention teaches that firstly the extent to which the fraction defective of a product is caused to increase by the structural conditions of a product under evaluation is estimated on the basis of the information concerning the contents of operations involved in the manufacturing works for manufacturing the product and the information concerning the properties of component parts for the product to be manufactured, and secondly the extent to which the manufacture-related fraction defective is caused to increase by the environmental conditions of the workshop destined for manufacturing the abovementioned product is estimated on the basis of the information indicating the facility status of that workshop for one or more workshop""s environmental conditions which provide the causes for failure occurrence, whereon the fraction defective which will be incurred when the above-mentioned product is manufactured in the above-mentioned manufacturing workshop is estimated.
The method of estimating to what extent the manufacture-related fraction defective is caused to increase by the structural conditions of the product under evaluation can be implemented in an exemplary implementation mode of the invention by arithmetically determining the estimated value of the fraction defective of the product on the basis of the information concerning the contents of operations involved in the manufacturing work (part attaching work in the case of an assembling work) and the information concerning the properties of the component part or parts.
To this end, in the case of assembling work, the species or types of operations required for specifying the contents of the operations involved in the part attaching works (operation for downward movement, operations for horizontal movements and the like which will collectively be referred to as the standard attaching operations) are determined, and numerical values indicating low or high probabilities of the standard attaching operations being not performed without fail under predetermined conditions including xe2x80x9ccondition imposed by a worker, conditions imposed by component parts and conditions imposed by a workshopxe2x80x9d (these conditions will be referred to as the standard conditions) is determined or set for each of the determined standard attaching operations. (The numerical values mentioned above will be referred to also as the standard-attaching-operation-based fraction defective coefficients.) Incidentally, by expressing the objective for evaluation in terms of a combination of the preset standard attaching operation elements, manipulability of a user interface could be enhanced. Furthermore, the present invention also teaches with a view to enhancing the accuracy of estimating the assembling-related fraction defective that in addition to the aforementioned standard attaching operation elements employed for taking into consideration the contents of attaching operations involved in the part attaching work, properties of the component parts (attachment-destined part and attachment-subjected part) which exert influence to the uncertainty of the attaching operation are expressed in terms of part-condition-related supplementary factors mentioned below, whereon the estimated value of the assembling-related fraction defective is arithmetically determined on the basis of the part-condition-related supplementary factors. More specifically, the factors exerting influence to the uncertainty of attaching work performed by a worker among the properties of the component parts (these factors will hereinafter be referred to as the part-condition-related supplementary factors) are determined, whereon for each of these influential factors as determined, a numerical value indicating the degree of the influence exerted by the influential factor to the attaching operation (this numerical value will hereinafter be referred to as the part condition supplementing coefficient) is determined. For the part attaching operation subjected to the assembling-related fraction defective estimation, the contents of the attaching operation are expressed by those preset part-condition-related supplementary factors which are pertinent to the properties of the component parts involved in the part attaching work of concern and which are selected from the preset part-condition-related supplementary factors mentioned above, in addition to the expression in terms of combination of the standard attaching operations as mentioned above.